Method of dosing mercury vapor lamps



Oct. 24, 1961 H. D. FRASER 3,005,674

METHOD OF DOSING MERCURY VAPOR LAMPS Filed Dec. 22, 1953 2 Sheets-Sheet 1 Ell/H067" Macs 1M:- 2L

INVENTORS. f/. a. five/r50? Oct. 24, 1961 H. D. FRASER ,0

METHOD OF DOSING MERCURY VAPOR LAMPS Filed Dec. 22. 1953 2 Sheets-Sheet 2 IN V EN TORj H. D. 79,

Unite States This invention relates to mercury vapor lamps and means and method of mercury dosing thereof, and more particularly in connection with high-intensity or highpressure type of lamps having quartz envelopes.

Double-wall lamps are known in the art, and while the present invention is essentially in such a lamp, the particular improvement relates primarily only to the inner bulb of such a lamp and the drawings therefore have been confined thereto. The single bulb completed with electrodes and dosage may be used alone as a lamp if desired. For more complete disclosure of the complete double wall lamp, reference may be had to application of Unglert et 211., SN. 113,444, filed August 31, 1949, and owned by the assignee of the present invention and now Patent No. 2,675,496 issued April 13, 1954. The envelope herein shown is the inner envelope for lamps of the character described and illustrated in said application.

In lamps of the character above referred to, the inner envelope or bulb is of quartz or hard glass, and contains a certain amount of mercury dosed into it during fabrication in order to attain the correct electrical char-v acteristics. The amount of mercury is highly critical and differs in each lamp, as the right amount depends upon the volume of the bulb interior and on the electrode spacing or arc length and on proper pressure to produce desired electrical characteristics. Heretofore, the correct dosing has been attempted by taking measurements of volume and arc length for each bulb and then from a table or chart determine the needful amount of mercury. The mercury then has to be measured and introduced in the determined quantity. Even in this step of introducing the mercury, inaccuracies occur not only in errors in measurement but also from failure of all of the measured amount of mercury to reach the interior of the bulb. Prior to this invention, the method followed required an intricate apparatus operating on the comparative pressure drop principle. The measurement of the arc length had to be done very accurately and the mercury had to be weighed on a very delicate balonce for each lamp. The tiny droplets of mercury were then placed in a capsule and inserted in the exhaustv tubulation. These several operations required the serv ices of several competent operators and represented possibility of numerous human errors resulting 'in unsatisfactory lamps.

In its broad aspect, therefore, the invention proposes elimination of the human element and development of means and method accurately productive of correctly dosed lamps.

Likewise of general nature, the invention contemplates governing the dosage electrically and individual to each lamp.

More spe ifi al y, an obj ct f the inv ti is. t

utilize the cha acteristics of each lamp. to d termine the requisite dosage with mercury present and function ng in the lamp and without having to take measurements of volume, arc length or dosage.

A furth r o j ct of the. invention is o ob ain a lame i h c te s ply me cu y h re n t mee h particular characteristiss f the lamp.

nother object o h n ion is to sp ed p odu ti n ater .A drop in voltage, with the and at the same time produce better lamps and with less labor than heretofore.

Again, an object of the invention is to provide simplified mechanism for producing accurately dosed mercury 1am s- Siill other objects of the invention will become apparout to persons skilled in the art to which it appertains as the description proceeds, both by direct recitation thereof and by inference from the context.

Referring to the accompanying drawings in which like numerals of reference indicate similar parts throughout the several views;

FIGURE 1 is an elevation, partly broken away, of a lamp in an intermediate stage of fabrication with its tubulation or arm intact therewith;

FIGURE 2 is an enlarged elevation of tubulation constricting means;

FIGURES 3, 4 and 5 show progressively steps in fabricating the lamp, and in particular FIG. 3 is an elevation "of a part-of the lamp showing its tubulation and constricting means therewith;

FIGURE 4 is a view similar to FIG. 3, showing an initial sealing of the tubulation following the exhaust, mercury dosing and gas-fill cycles;

FIGURE 5 is a view similar to FIGS. 3 and 4, and showing the constricting means being effectuated;

FIGURES 6 and 7 are views at right angles to each other showing a machine for subjecting the lamp to heat treatment for proper dosing thereof;

FIGURE 8 is a View of the lamp as closed and ready to seal oil;

FIGURE 9 is a view of the lamp for use. i

For a general understanding of the invention, it may be preliminarily stated that since the voltage of the lamp of the character here involved depends upon the mercury pressure and the amount of mercury required depends in part upon the pressure, it is expedient to first overdose the lamp and thereafter reduce the dosage agreeableto the various parameters of pressure, electrode spacing volume and voltage requirements under existing conditions for the particular lamp. The greater the amount of mercury for a given volume, the higher the voltage. Therefore, we pre-dose the lamp with an amount of mercury in excess of the maximum amount ever needed for a given voltage and for maximumvolumes andarc length possibly encountered in a series of lamps being fabricated.-

The lamp is first exhausted and baked, after which it is pro-dosed with mercury as above stated and charged with a small amount of more readily ionizable gas, such as argon. The tabulation is then closed at a distance from the lamp and the constriction made efiective.

sealed off and ready Thereafter the envelope is heated to fully vaporize themercury, which of course produces pressure in proportion to the amount of mercury present. The electrodes are connected to an electric circuit supplying an over voltage thereto so-as to produce a discharge therebetween. The tubulation is maintained cooler than the envelope and therefore mercury vapor will condense in the tabulation, thereby lowering the vapor pressure in the envelope.

lamp operating, automatically accompanies the drop in pressure until the voltage finally comes down to the desired rating for the lamp. At this stage, the tubulation is sealed off next to the envelope so the condensed mercury cannot return to the envelope, and thus the lamp is completed having a properconnection forming part. of the exhaust machine.

in operation, the pressure created by the vaporization 7 portion having amain electrode 12 therein. A starting electrode 13 is also located in one of said reduced end portions. The 'termiriationof the reduced portions is pressed, as at 14, iuto'se'aling engagement with lead-in connections 15 for the electrodes all in accordance with usual lamp practice. The electrodes are made electron emissive, and for that purpose, and by way of example, may be tungsten coated with barium oxide. The envelope thus described is a sealed enclosure, but for exhaust and other purposes, has a tubulation 16 opening thereinto during fabrication, said tubulation being sealed when the need for access to the interior ceases and before the lamp is put into service, but during fabrication the tubulation is retained .and utilized-as will presently appear. The lamp as constructed up to this stage may, for convenience, be referred to as the embryonic lamp. Our invention is concerned with the completion ofthe lamp frorn this embryonic stage. 7

The tubulation 16 is prepared for its intended service by first having a constricting means 18 inserted therein, said meansbeing illustrated in the present showing as a cane-like length of twisted wire having a hooked end with adequate resiliency to frictionally retain the wire at the position to which it is mechanically pushed when inserted. Said means is shoved into the tubulation to a placenear the junction of the tubulation with the envelope and at a greater distance from the other or outer. end of the tubulation. There is adequate space around this constricting means within the passageway of the tubulation to both pass gas and liquid mercury. The envelope is first exhaustedby connecting the outer end of said tubulation to an exhaust machine, as indicated in FIG. 3,'and is also baked. I a a The next step in the method employed is to introduce a quantity of mercury into the envelope which of course can be done byway of the tubulation and a usual valved The amount of mercury is in excess of any possible need that maximum tolerances ofaenvelope volume and electrode spacing for a run of lamps would ever requirej A large drop 17 of mercury'is indicated in FIGURE as representative of this excess mercury loading. Following this mercury introducing or loading step, the envelope is charged with a small amount of ionizable gas, such as argon, introduced through said tubulation in usual manner before the tubulation is disconnected from the exhaust machine, an appropriate valve and connections for the purpose constituting part of that machine.

The tubulation is next given an initial seal-01f 20 from the exhausting machine, as indicted, accomplished by gas flames 21 shrinking the tubulation glass in FIG. 4. This initial seal-off 20 is atthe far side'of the constricting means 18 away from the lamp and at a considerable distance from said constricting means so that this section 22 of the tubulation between said means 18 and seal-0E 20 will have. a considerable capacity for mercury, will present a considerable cooling area, and will project out of the envelope baking oven in a subsequent step as will be described below.

The next step in fabrication, either before or after performing the above described step is to effectuate the constrictingmeans whereby vaporized'mercury may pass the same but liquified mercury cannot. .As shown in FIG. 5, the glass wall of the tubulation proximate to said constricting means 18 is heated, as by gas flames 19, V I to, soften the glass and shrink the tubulation as at 18a' into contact with said means, but not so tightly that gas cannot pass the constriction. The use of twisted wire as the constricting means isadvantageous in maintaining an adequate gas-passing crevice from end to end thereof.

The lamp as thus partially completed and with its long tubulation divided internally by the gas-passing liquid barring constriction will be referred to herein as in its rudimentary stage or condition as it is charged with a starting gas, loaded with liquid mercury, and sealed and therefore will support an arc discharge across its electrodes. As the lamp in this rudimentary stage is sealed-off at the outer end of the'tubulation, it constitutes a complete article of manufacture on .which further Operations may be performed at another time and place,

and for certain purposes is usable in. the rudimentary stage. However, in this rudimentary stage, thelamp has an excess of mercury therein for its volume and electrode spacing to function at the desired voltage rating.

A dosage limiting or regulating step is next performed to eliminate the excess of the mercury loading and confine the mercury dosage retained to the precise amount requisite to the particular lamp. 'In performance of this step, apparatus such as illustrated in FIGURES 6 and 7 may be utilized. This is.s hown as an axially horizontal cylindrical oven 23 comprising two sectionsconstituted by semi-cylindrical gas manifolds 24, 24 which can be separated both to admit or remove the lamp and to discontinue application of heat to the envelope at the proper moment. The specific arrangement illustrated provides a fixed support 25 carrying tracks 26 beneath the oven and transverse to the axis thereof. wheels 28 riding on saidtracks ha ve stanchions 29 in which rigid gas supply pipes 30 are firmly secured firmly supporting the oven sections. Each pipe 30 has a flexible feed pipe 31 thereto enabling the trucks to be moved on their tracks. At the ends of the oven are brackets ,32 from support 25 enabling the lamp to be held coaxially within the oven and to remain stationaryirrespective of movement of the oven sections. The arrangement permits .the sections to be readily moved apart and the gas supply may be manually or automatically reduced, if de sired, at such time. However, the retraction of the flames from vicinity of the lamp is ordinarily suificientto serve the purposes of the invention for heat reduction.

Automatic means are preferably provided to etfectthe heat reduction at the proper time. For this purpose a solenoid core 33 is shown parallel to the tracks 26 and fixed on the stanchions 29 projecting in directions away from. the oven, Fixed coils 34 are associated with said cores so that when the coils'are excited the trucks and oven sections supported thereby will be retracted from the lamp a distance indicated by dimension line 35 in FIG. 7. The purpose of applying heat by the oven upon the lamp is to vaporize the mercury and. of course the mercury vapor increases the pressure within the tube. Mercury vapor will consequently pass the tubulation re: striction 18 and enter the outer section 22 of the tubulation which projects outside of the oven. While the fact that this section of the tubulation is outside of the oven is ordinarily sufiicient to keep it relatively cool, an air nozzle 36 may be provided to promote heat exchange and thereby assure that vapor in said section will be con densed. As fast as it condenses the pressure is reduced and more vapor will enter through the constriction. As the constriction cannot pass liquid mercury, the condensed mercuryin tubulation section 22 cannot return to the lamp envelope and, consequently, the mercury vapor and pressure in the envelope become progressively less and soon will be reduced to the desired value or desideratum.

In order that the quantity of mercury shall not be reduced more than just to the desired and proper'amount, automatic means are provided for operation of the aforementioned solenoids for thereby retracting the oven sections and stop the further extrusion'of' mercury vapor Trucks 27, with through the constriction. For this purpose the lead-in connections, and therefore electrodes 12, 13 are incorporated in an operating electric circuit 3'7. Since the vapor pressure is high, the lamp voltage will also be high and will reduce as the pressure is lowered by the above described baking. An instrument 38 is connected in shunt across the circuit feeding the electrodes, this instrument having a construction corresponding to a voltmeter so that a hand 39 or other movable part is moved to different positions for different values of voltage. As shown, the hand swings to the right as voltage goes to maximum and swings back to the left or anti-clockwise as the voltage reduces. The instrument also includes a contact 4b which closes a line 41 from the power source 42 to the solenoids 34 at the desired voltage for proper operational purposes for the lamp arc. Thus the lamp, as soon as the voltage becomes right therefor, has the applied heat retracted and the mercury therein is not further depleted but thereafter remains constant in proper amount. Fires (not shown) are then applied at the base of the tubulation next to the lamp and below the constriction and the tubulation sealed off, as at 43, completing the lamp. As the lamp cools, the mercury therein condenses and as shown by the smaller drop of mercury 44 in FIGS. 8 and 9, has the proper amount incorporated therein to supply mercury vapor and pressure in the lamp for future operation in use precisely correct for that particular lamp and so it will operate at a standardized volage rating.

It is not amiss to add that for the specific disclosure a switch 45 is desirably included in the circuit from the instrument 38 to the solenoids so as to avoid operation of the solenoids on the clockwise advance of the instrument hand, said switch being closed after the hand has passed contact 4%) whereby the closing of the circuit to the solenoid occurs only on the return swing of said hand. Such a switch may be made to operate either manually or automatically.

I claim:

1. A method of lamp fabrication from its embryonic stage wherein a mercury loaded lamp envelope has a tribulation thereon, comprising sealing-off the outer end of said tubulation, vaporizing the mercury in the envelope and condensing a part thereof in said tabulation, and sealing-off the tabulation at its end next to the envelope.

2. A method of lamp fabrication from its embryonic stage wherein a mercury loaded lamp envelope has a tubulation thereon, comprising constricting the tubulation intermediate of its ends sufficient to prevent passage of liquid mercury but capable of passing mercury vapor, vaporizing the mercury in the envelope and condensing a part thereof beyond said constriction, and sealing-off the tubulation between the envelope and constriction.

3. A method of lamp fabrication from its embryonic stage wherein a mercury loaded lamp envelope has a tubulation thereon, comprising exhausting said envelope and initially sealing the tubulation at a distance from the envelope, constricting said tubulatio-n intermediate of its ends suffifiicient to prevent passage of liquid mercury but capable of passing mercury vapor, vaporizing the mercury in said envelope and condensing the part thereof passing said constriction and thereby reducing the vapor pressure in the envelope to a desideratum, and sealing the tubulation between the lamp envelope and the tabulation constriction.

4. A method of lamp fabrication from its embryonic stage wherein a lamp envelope has a tubulation thereon,

comprising inserting a constriction into the tubulation at a distance from the outer end thereof, exhausting said envelope, dosing the envelope with mercury, initially sealing the tabulation beyond said constriction, vaporizing the mercury in said envelope and condensing the part thereof passing said constriction and thereby reducing the vapor pressure in the envelope to a desideratum, and sealing the tubulation between the lamp envelope and said constriction.

5. A method of lamp fabrication from its embryonic stage wherein a lamp envelope has a tubulation thereon, comprising inserting a constriction into the tubulation at a distance from the outer end thereof, exhausting said envelope, dosing the envelope with mercury, initially sealing the tabulation beyond said constriction, sh1ink ing the tubulatio-n around said constriction but leaving crevices sufficient for mercury vapor to pass the con striction, vaporizing the mercury in said envelope and condensing the part thereof passing said constriction and thereby reducing the vapor pressure in the envelope to a desideratum, and sealing the tubulation between the lamp envelope and said constriction.

6. A method of lamp fabrication from its embryonic stage wherein a lamp envelope has a tubula-tion thereon and has electrodes therein complete with lead-in wires sealed through the envelope, comprising exhausting the envelope, dosing the envelope with mercury, sealing-oil the tubulation at its outer end at a distance from the envelope, applying current to the electrodes and obtaining arc discharge therebetween, vaporizing the mercury in said envelope and condensing a part thereof in the tubulation to a desideratum of voltage requirement for the arc discharge, immediately discontinuing vaporizing of the mercury and promptly sealing the tabulation with the condensed mercury excluded from the envelope.

7. A method of lamp fabrication from its embryonic stage wherein a mercury loaded lamp envelope has a tabulation thereon and has electrodes therein complete with lead-in wires sealed through the envelope, comprising constricting said tabulation intermediate of its ends sufiicient to prevent passage of liquid mercury but capable of passing mercury vapor, applying current to the electrodes and obtaining arc discharge therebetween, applying heat to vaporize the mercury in said envelope, maintaining the outer end of said tubulation beyond said constriction cool and condensing the part of the mercury vapor passing said constriction and thereby reducing the vapor pressure in the envelope to a desideratum of voltage requirement for the arc discharge, means for discontinuing the application of vaporizing heat to the mercury in the envelope when said desideratum of voltage requirement is reached, and thereupon sealing the tubulation between said envelope and constriction.

References Cited in the file of this patent UNITED STATES PATENTS 2,200,221 Swinehart et a1. May 7, 1940 2,208,113 Bonney et al July 16, 1940 2,284,036 1301 May 26, 1942 2,311,930 Chirelstein Feb. 23, 1943 2,398,340 Wilder Apr. 9, 1946 2,456,396 Frohock Dec. 14, 1948 2,476,387 Rooves July 19, 1949 2,491,874 Penon Dec. 20, 1949 2,666,545 Hopfield Jan. 19, 1954 2,730,424 Kenty et a1. Jan. 10, 1956 

